[Wasm] Support callable references to external functions

1. Move jsInteropFunctionsLowering after callable reference lowering,
  so it can continue to deal with just functions and function calls.
2. Generate lowered closure class in JsInteropFunctionsLowering because

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/WasmLoweringPhases.kt

@@ -504,9 +504,6 @@ val wasmPhases = NamedCompilerPhase(
             excludeDeclarationsFromCodegenPhase then
             expectDeclarationsRemovingPhase then
 
-            jsInteropFunctionsLowering then
-            jsInteropFunctionCallsLowering then
-
             // TODO: Need some helpers from stdlib
             // arrayConstructorPhase then
             wrapInlineDeclarationsWithReifiedTypeParametersPhase then
@@ -535,6 +532,9 @@ val wasmPhases = NamedCompilerPhase(
             delegateToPrimaryConstructorLoweringPhase then
             // Common prefix ends
 
+            jsInteropFunctionsLowering then
+            jsInteropFunctionCallsLowering then
+
             enumEntryInstancesLoweringPhase then
             enumEntryInstancesBodyLoweringPhase then
             enumClassCreateInitializerLoweringPhase then

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/lower/JsInteropFunctionsLowering.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.backend.wasm.lower
 
 import org.jetbrains.kotlin.backend.common.BodyLoweringPass
 import org.jetbrains.kotlin.backend.common.DeclarationTransformer
+import org.jetbrains.kotlin.backend.common.ir.createImplicitParameterDeclarationWithWrappedDescriptor
 import org.jetbrains.kotlin.backend.common.ir.createStaticFunctionWithReceivers
 import org.jetbrains.kotlin.backend.common.lower.DeclarationIrBuilder
 import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
@@ -14,17 +15,13 @@ import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
 import org.jetbrains.kotlin.backend.wasm.ir2wasm.isBuiltInWasmRefType
 import org.jetbrains.kotlin.backend.wasm.ir2wasm.isExported
 import org.jetbrains.kotlin.backend.wasm.ir2wasm.isExternalType
-import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
+import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.ir.backend.js.utils.getJsNameOrKotlinName
 import org.jetbrains.kotlin.ir.builders.*
-import org.jetbrains.kotlin.ir.builders.declarations.addValueParameter
+import org.jetbrains.kotlin.ir.builders.declarations.*
-import org.jetbrains.kotlin.ir.builders.declarations.buildFun
+import org.jetbrains.kotlin.ir.declarations.*
-import org.jetbrains.kotlin.ir.declarations.IrClass
-import org.jetbrains.kotlin.ir.declarations.IrDeclaration
-import org.jetbrains.kotlin.ir.declarations.IrDeclarationParent
-import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
 import org.jetbrains.kotlin.ir.expressions.*
-import org.jetbrains.kotlin.ir.expressions.impl.IrFunctionExpressionImpl
+import org.jetbrains.kotlin.ir.expressions.impl.IrInstanceInitializerCallImpl
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
@@ -386,46 +383,73 @@ class JsInteropFunctionsLowering(val context: WasmBackendContext) : DeclarationT
             name = Name.identifier("f")
             type = context.wasmSymbols.externalInterfaceType
         }
-        val builder = context.createIrBuilder(result.symbol)
+
-        val backendContext = context
+        val closureClass = context.irFactory.buildClass {
-        result.body = builder.irBlockBody {
+            name = Name.identifier("__JsClosureToKotlinClosure_${info.hashString}")
-            val lambda = context.irFactory.buildFun {
+        }.apply {
-                name = Name.identifier("kotlinClosure_${info.hashString}")
+            createImplicitParameterDeclarationWithWrappedDescriptor()
-                returnType = info.originalResultType
+            superTypes = listOf(functionType)
+            parent = currentParent
         }
-            lambda.parent = result
+
-            val lambdaBuilder = backendContext.createIrBuilder(lambda.symbol)
+        val closureClassField = closureClass.addField {
+            name = Name.identifier("jsClosure")
+            type = context.wasmSymbols.externalInterfaceType
+            visibility = DescriptorVisibilities.PRIVATE
+            isFinal = true
+        }
+
+        val closureClassConstructor = closureClass.addConstructor {
+            isPrimary = true
+        }.apply {
+            val parameter = addValueParameter {
+                name = closureClassField.name
+                type = closureClassField.type
+            }
+            body = context.createIrBuilder(symbol).irBlockBody(startOffset, endOffset) {
+                +irDelegatingConstructorCall(context.irBuiltIns.anyClass.owner.constructors.single())
+                +irSetField(irGet(closureClass.thisReceiver!!), closureClassField, irGet(parameter))
+                +IrInstanceInitializerCallImpl(startOffset, endOffset, closureClass.symbol, context.irBuiltIns.unitType)
+            }
+        }
+
+        closureClass.addFunction {
+            name = Name.identifier("invoke")
+            returnType = info.originalResultType
+        }.apply {
+            addDispatchReceiver { type = closureClass.defaultType }
             info.originalParameterTypes.forEachIndexed { index, irType ->
-                lambda.addValueParameter {
+                addValueParameter {
                     name = Name.identifier("p$index")
                     type = irType
                 }
             }
-            lambda.body = lambdaBuilder.irBlockBody {
+            val lambdaBuilder = context.createIrBuilder(symbol)
+            body = lambdaBuilder.irBlockBody {
                 val jsClosureCallerCall = irCall(jsClosureCaller)
-                jsClosureCallerCall.putValueArgument(0, irGet(result.valueParameters[0]))
+                jsClosureCallerCall.putValueArgument(0, irGetField(irGet(dispatchReceiverParameter!!), closureClassField))
                 for ((adapterIndex, paramAdapter) in info.parametersAdapters.withIndex()) {
                     jsClosureCallerCall.putValueArgument(
                         adapterIndex + 1,
                         paramAdapter.adaptIfNeeded(
-                            irGet(lambda.valueParameters[adapterIndex]),
+                            irGet(valueParameters[adapterIndex]),
                             lambdaBuilder
                         )
                     )
                 }
                 +irReturn(info.resultAdapter.adaptIfNeeded(jsClosureCallerCall, lambdaBuilder))
             }
-            +irReturn(
+
-                IrFunctionExpressionImpl(
+            overriddenSymbols =
-                    UNDEFINED_OFFSET,
+                overriddenSymbols + functionType.classOrNull!!.functions.single { it.owner.name == Name.identifier("invoke") }
-                    UNDEFINED_OFFSET,
-                    functionType,
-                    lambda,
-                    origin = KOTLIN_WASM_CLOSURE_FOR_JS_CLOSURE,
-                )
-            )
         }
 
+        val builder = context.createIrBuilder(result.symbol)
+        result.body = builder.irBlockBody {
+            +irReturn(irCall(closureClassConstructor).also { it.putValueArgument(0, irGet(result.valueParameters[0])) })
+        }
+
+        additionalDeclarations += closureClass
         additionalDeclarations += result
         return result
     }

compiler/testData/codegen/boxWasmJsInterop/functionTypes.kt

@@ -199,9 +199,25 @@ fun box(): String {
     )
     if (externalWithLambdas2Count != 11) return "Fail externalWithLambdas2"
 
+    val externalWithLambdas2Ref = ::externalWithLambdas2
+    val externalWithLambdas2RefCount = externalWithLambdas2Ref.invoke(
+        { true },
+        { 100.toByte() },
+        { 200.toShort() },
+        { 'я' },
+        { 300 },
+        { 400L },
+        { 500.5f },
+        { 600.5 },
+        { "700" },
+        { create123Array() },
+        { DC(800, 800) },
+        { it.y }
+    )
+    if (externalWithLambdas2RefCount != 11) return "Fail externalWithLambdas2"
 
-    val jsLambda = createJsLambda()
+    val createJsLambdaRef = ::createJsLambda
-
+    for (jsLambda in arrayOf(createJsLambda(), createJsLambdaRef.invoke())) {
         val jsLambdaCount = jsLambda(
             true,
             100.toByte(),
@@ -218,6 +234,7 @@ fun box(): String {
         )
         if (jsLambdaCount != 11)
             return "Fail 3"
+    }
 
     complexHigherOrerTest()